Couple of weird things I noticed:
Borderlands 3 says it's 50% off and the sale price is £44.99 -
Borderlands 3 Price says full price is £59.99 and that it's not actually on sale at all (neither does Xbox.com)
Also
FAR CRY 4 Valley of the Yetis is showing as 70% off for £7.19 but the game page shows it as £4.79 - full price is £11.99 so I'm guessing the game page is the correct one. Xbox.com shows it at £4.79 but says that it's 60% off.
Like I say, weird ....
There may be more, they are just ones I saw